The use of microwave ovens in home cooking has been steadily increasing. It has become highly desirable, therefore, to package food products, and particularly shelf-stable and frozen food products, in containers or cartons which are suitable for heating or cooking of the food in the carton. Moreover, it is highly desirable if the carton may optionally be used as a mixing and serving dish.
As is the case in general with packaging, it is also a very important aspect of any container that the cost of the container be minimized. Thus, cartons for food and non-food products which require expensive or costly equipment to effect folding or folding cycle times which are relatively long will result in an undesirably high carton cost. Similarly, cartons which are formed from separate components and/or inserts that are adhesively secured together usually are undesirably costly to manufacture.
A standard approach to the formation of cartons is to provide flaps or tabs which can be used in combination with various fold lines to secure the sides and top of a carton together. The technique of using tabs or flaps to form a carton, however, requires that the sidewalls and bottom of the carton be held in an indexed or squared relationship during the process of adhesively securing the tabs or flaps in place. Such indexing can be accomplished, but it also increases the cycle time for formation of a carton from a carton blank. This same component indexing problem occurs when cartons are formed from two or more pieces that are adhesively secured together.
Typical of a prior art foldable microwave carton is the carton shown in U.S. Pat. No. 4,687,104. The carton is formed from a one-piece blank in which the bottom and sidewalls are folded up while the top with associated flaps are folded down to form the carton. The top also includes a reverse cut flap which can be opened to allow the user to eat food directly from the carton. The carton is constructed, however, so that upon opening of the reverse cut flap there remains a U-shaped lip around the top of the carton, which provides structural integrity, but also inhibits eating directly from the carton. Moreover, the level of food in the carton will normally be substantially at the level of the opening. Thus, adding ingredients to such cartons, using the carton as a mixing container, and cooking with the top removed and without spatter from the carton, is not practical.
U.S. Pat. No. 4,586,648 discloses a tray-like carton in which the sidewalls of the carton include a tapered section and an upwardly extending lip or skirt section. This carton is formed from a single piece blank, but the upper carton extension is secured through the use of flaps which are adhesively joined to the extension panels, which requires indexing or folding of the carton while held in the square relationship. Moreover, the extension on the tray-like carton always remains in an extended position and a lid is mounted to the top of the carton. While a carton of this type provides greater access to its contents, if the carton is filled to the top of the extension, cooking with the top off and without spatter is not possible, and spilling from the carton when it is used as a serving tray or dish is not unlikely.
U.S. Pat. No. 2,917,221 discloses a foldable carton or container having sidewalls and an extension which can be folded between an extended position above the side wall panels and an inwardly folded position generally parallel to the bottom panel. Again, however, the carton is die cut so that the end walls of the carton are free flaps which must be held in a squared-up relationship during carton forming. Additionally, die cuts extend completely to the bottom wall of the carton, making the carton poorly suited for use with food products containing liquids, which can leak from the corners of the carton.
A similar carton structure is shown in U.S. Pat. No. 3,581,977, but folding and formation of the carton is accomplished by reducing the number of seams at which leakage can occur to one. This, again, requires squaring-up of the carton during the tab sealing process, and the carton still contains one vertically extending seam which can be the source of leakage. Other tray-like cartons are disclosed in U.S. Pat. Nos. 3,316,102; 3,829,003 and 4,344,537. Generally, these foldable cartons lack a skirt above the sidewalls which will permit the adding of ingredients, allow mixing in the carton and prevent spilling of the contents during eating directly from the carton. Formation of such cartons also may depend upon holding the carton in a square relationship during the folding process so that free tab ends can be adhesively secured in the proper position.
Other foldable cartons which depend upon squaring-up and holding of the carton walls in position during the sealing of flaps in place are disclosed in U.S. Pat. Nos. 3,655,155; 3,750,932; 3,780,932; 3,913,823; 3,964,668; 4,036,423; 4,184,597; 4,586,649 and 4,687,130. Finally, U.S. Pat. No. 4,216,861 discloses a folded tubular carton in which an opening is employed to provide a structure for locking end flaps in place to avoid the necessity of gluing. This carton, however, is not suitable for use as a serving tray, does not include an extension to prevent the spilling of contents, and the openings in the carton walls are positioned so as to be a potential source of leaks in the event that liquids were to be heated in the carton.
Accordingly, it is an object of the present invention to provide a foldable carton which is suitable for use for storing a variety of food and non-food products and further can be used for mixing, microwave cooking and serving of food products therefrom.
Another object of the present invention is to provide a foldable carton which will automatically square itself up during the forming process so as to eliminate the need for indexing of tabs and to reduce the cycle time required to effect folding.
Still a further object of the present invention is to provide a foldable carton having an extension or skirt above the sidewalls which will reduce the chance of spatter during cooling with an open top and spilling of the contents when eating directly from the carton.
Another object of the present invention is to provide a foldable carton having an extension which enables the addition of ingredients to the carton and mixing prior to and during cooking.
Another object of the present invention is to provide a foldable, tray-like carton which is impervious to leakage of liquid contents therefrom during microwave cooking.
A further object of the present invention is to provide a foldable carton which can be used as a set-up carton that can be shipped flat and set-up by a merchant to be used as a container for the merchant's products.
Still a further object of the present invention is to provide a foldable carton which is less expensive to form, has improved strength and durability, and is easy to open and use.
The foldable carton of the present invention has other objects and features of advantage which will become apparent from and are set forth in more detail in the accompanying drawing and following description of the Best Mode Of Carrying Out The Invention.